The Evolved UMTS (Universal Mobile Telecommunications System) Radio Access Network (E-UTRAN) is the air interface of the 3GPP Long Term Evolution (LTE) expansion of the wireless communication protocol. E-UTRAN is expected to continuously increase the number of frequency bands utilized for wireless communications. Furthermore, there is expected to be some degree of overlap with other (i.e., new or legacy) E-UTRA frequency bands.
EARFCNs are channel numbers that reflect the center frequency of an E-UTRAN carrier, which may occupy, e.g., 1.4, 3, 5, 10, 15, or 20 MHz, independent of the channel spectrum of the E-UTRAN carrier, which are discussed, for example, in 3GPP TS 36.101 Ver. 11.9.0.
To uniquely identify all anticipated E-UTRAN carriers, 3GPP has agreed to extend the range of EARFCN values from 65535 (i.e., 216 from 16 bits) to 262143 (i.e., 218 from 18 bits). This allows for a quadrupling of the EARFCN value range, increasing by nearly 4× the number of E-UTRAN carriers that can be identified, although some EARFCN values may be reserved. E-UTRAN-capable User Equipment (UE) that supports an extended EARFCN value range will operate in an E-UTRAN network.
As UE technology advances, many UEs are capable of operating in networks employing any of several different Radio Access Technologies (RATs). These UEs are referred to herein as multi-RAT-capable UEs. For example, a multi-RAT-capable UE may operate in either a GERAN or E-UTRAN network.
One challenge is how to signal EARFCN values within the extended EARFCN value ranges in GERAN to inter-RAT-capable UEs to support continued inter-RAT mobility between GERAN and E-UTRAN networks.
The Background section of this document is provided to place embodiments of the present invention in technological and operational context, to assist those of skill in the art in understanding their scope and utility. Unless explicitly identified as such, no statement herein is admitted to be prior art merely by its inclusion in the Background section.